Module Core_kernel.Total_map

A map that includes an entry for every possible value of the key type.

This is intended to be used on 'key types where there is a full enumeration of the type. In the common use case, 'key will be a simple variant type with [@@deriving compare, enumerate]. For example:

      module Arrow_key = struct
        module T = struct
          type t =
            | Up
            | Down
            | Left
            | Right
          [@@deriving sexp, bin_io, compare, enumerate]
        end
        include T
        module Total_map = Total_map.Make (T)
      end

In such a case, a t is semantically equivalent to a pure function from 'key to 'value. The differences are that it is serializable and that mapping or changing a t will produce a t using the same amount of space as the original.

However, in theory you could also modify the comparison function and enumeration, so long as the enumeration contains at least one representative of each equivalence class determined by the comparison function.